Now the reference is to the great Willie Mays falling down in center field trying to catch a fly ball.

Or to Joe Louis entering the ring one time too many - and leaving it through the ropes after getting knocked out by Rocky Marciano.

Those were sad moments in sports.

As bad as Woods looked over two days at the PGA Championship, it would be premature to say this was another one. But it sure looked that way.

Really, was it any worse than three years ago at the PGA Championship?

Woods missed two majors in the summer of 2011 to let his leg injuries heal, the ones that caused him to withdraw after nine holes and a 42 at The Players Championship.

He returned to finish 18 shots out of the lead at Firestone and then missed the cut at the PGA Championship by six shots. He was 35. Now he's 38.

It had been three years since he last won a major. Now it's six.

He had played only one event heading into the final major of the year in 2011, never shot worse than 72 and tied for 37th.

This time, Woods was returning from back surgery that kept him out of the Masters and US Open.

He had three starts before the final major - including the British Open. He missed the cut by four shots, had his worst 72-hole finish in a major and withdrew from the final round at Firestone with a different back injury.

And then he waited until the last day to show up at Valhalla, played nine holes of practice and couldn't beat five club pros.

Woods said he was pain-free after playing nine holes on Thursday (NZ time). He said his back was a little stiff after a 74 on Friday. And he said his back ''went out on me'' on the range and ''I just had to play through it'' on his way to another 74.

''I just noticed that really on the greens the ball wasn't going in the hole.'' Ouch.

The trouble assessing injuries is that only the athlete knows how bad it hurts. It's even more complicated when the athlete - Woods - isn't forthcoming about it.

Is this the end? Not yet.

But it most likely is the end of Woods as golf once knew him. The end of a guy who once won seven out of 11 majors, and who got to 79 wins on the PGA Tour more quickly than anyone in history.

Woods always talked about his pursuit of Nicklaus and the record 18 professional majors as a marathon. He's approaching Heartbreak Hill with four knee surgeries and back problems that keep cropping up.

''I've won tournaments when I wasn't playing my best. If I play my best and don't win, there's no reason to be out here.''

They all say that. But how do they really know?

Football players lose a step. A great hitter doesn't see the ball quite as well.

Golfers don't make as many putts.

''You'll know when I'm not able to produce any more,'' Woods said that day.

''I don't lie. When I play well, I tell you guys. When I haven't played well, I'll tell you.''

All he could say yesterday at Valhalla was, ''I tried as hard as I could. That's all I've got.''

He is four PGA Tour wins away from breaking the record of Sam Snead (82). He is five majors away from breaking the major championship record by Nicklaus (18).

Woods has been stuck on 14 majors since 2008 at the U.S. Open.

Woods did win five times last year before back trouble began to take its toll. Don't give up on him just yet. But each year he gets older, and someone new comes along.

Rory McIlroy played his first pro event in America the same week Woods returned from reconstructive knee surgery. Jordan Spieth showed up in a big way last year.

It's not getting any easier.

The plan for Woods was to spend his time off getting stronger in his core muscles. Woods talks about not burning the candle at both ends - working in the gym and working at golf. His biggest rival now might be time.